Coupling electrocoagulation with electro-oxidation for COD and phosphorus removal from industrial container wash water

Abstract

• A process was developed for treatment of industrial container wash water (IWW). • Electrocoagulation (EC) and electrooxidation (EO) processes were successively used. • Optimum operating parameters of individual and coupled EC and EO were compared. • EC-EO combination allowed the removal of 97% of phosphorus and 95% of COD. • EC-EO combination reduced the treatment cost around 3.3 times than individual EO. Electrochemical processes such as electrocoagulation (EC) and electrooxidation (EO) have proved their effectiveness for the treatment of industrial refractory wastewater. This study aimed to strategically combine EC and EO processes for the treatment of highly contaminated wastewater (COD of 10,360 ± 665 mg/L and phosphorus concentration of 22.9 ± 0.9 mg/L) coming from industrial container wash water (IWW). In this regard, the EO and EC processes were investigated individually and then in combination. For the EO process, different operating parameters were investigated such as the type of anode, current density, type of electrolyte, amount of electrolyte, treatment time, and contamination concentration, while for the EC the current density and pH were studied. Although EO process decreased up to 91 ± 4.9% of COD, this process did not allow to reach the guideline (800 mg/L of COD) required for effluent discharge in the sewage urban networks. This was mainly attributed to the presence of phosphate ions which are known as hydroxyl radical scavengers. EC process was then firstly used as pre-treatment to remove phosphate ions from IWW, followed by EO process. The EC-EO combination allowed 97% and 95% of phosphorus and COD removal to meet the sewer discharge standard, respectively. A cost analysis showed that the EC-EO coupling reduced the operating costs to 7.3 CAD $/m 3 compared to 24 CAD$/m 3 recorded while EO process was used alone for the treatment of IWW.